Control systems incorporating PLCs (Programmable Logic Controlers) and DCSs (Distributed Control Systems) are frequently used to control real world processes by accepting inputs which typically originate from sensors such as, among others, those used to sense temperature, flow, level, radiation, light, movement, and pressure, and those used in generating outputs which are used to drive actuators such as hydraulic devices, valves, lights, and motors. Control systems can often be viewed as having a control component and an interface component, with one or both components having both hardware and software sub-components. Thus a PLC based device might utilize a digital PLC having embedded software as the control component (the “controller”), with an interface component (the “I/O interface”) (a) accepting signals from sensors and converting them into a form acceptable to the PLC, and (b) accepting outputs from the PLC and converting them to signals suitable as inputs to the actuators. In such systems, the controller and I/O interface are often connected by one or more paths (the “controller-I/O communication channel) to allow communication and control signals to pass between the controller and the I/O interface. Similarly, the I/O interface is, after the control system is installed in its operating environment, connected via one or more electrical paths (the “field wiring”) to the components from which the control system receives its inputs, and to the components to which the control system directs its outputs, with the I/O interface being provided with a plurality of connectors (“field I/O connectors”) which facilitate connecting the I/O interface with the field wiring. Many control systems will also incorporate a human-machine-interface (HMI) component comprising hardware and or software for facilitating operator interaction with the control system.
Although methods and devices for testing control systems are known, they generally have individual strengths and weaknesses which make them more appropriate in some situations and less appropriate in other. Thus, there is a continuing need for improved methods and apparatus for control system testing.